Lifting construction for helicopter



Jan. 4, 1966 P, You

LIFTING CONSTRUCTION FOR HELICOPTER 2 Sheets-Sheet 1 Filed April 17,1964 lM/f/VTOR fi'erre Y0 U ATTORNEYS Jan. 4, 1966 P. You 3,227,220

LIFTING conswnucnon FOR HELICOPTER Filed April 17, 1964 2 Sheets-Sheet 2Pierre 701/ 7. y

% Arron/VH5 United States Patent Ofiice 3,227,220 Patented Jan. 4, 1966The present invention relates to a helicopter and more particularly to anovel lifting construction therefor.

The device or construction of the invention is designed to improve thestability in helicopters by reducing the flapping effect of the wingblades. As is known, this flapping effect results from the difference inthe lifting forces acting on a forward moving blade and a rearwardmoving blade disposed 180 from the former. This difference in liftingforces is of course due to the fact that with both blades given the sameangle of incidence and with one blade travelling against the wind whilethe other travels with the wind, the general tendency is, therefore, toslant downwardly in the direction of the blade moving with the wind, theamount of slanting increasing from practically nothing when the bladesare lengthwise in the Wind to a maximum when they are crosswise in thewind; the net result being the effect known as flapping which insofar asstability of the helicopter isconcerned, is the number one problem. Noadequate solution has yet been proposed to overcome this difliculty.

It is, therefore, a main object of the invention to provide a liftingconstruction for helicopter wherein the. flapping efiect normallyencountered in conventional heliblades are unequal; the equalizationbeing obtained by causing automatic adjustment of the angles ofincidence of the blades as theyrotate around the rotor mast.

The above objects may be obtained in a helicopter equipped with alifting construction according to the invention which comprises: acentral lifting rotor; a rotary member mounted on each side of therotor; a blade mounted on each side of the rotor and having a leadingedge and an axis of lift; a shaft secured on the inboard end of eachblade and mounted on one of said members for rotation relative theretoabout an axis parallel to and between the axis of lift and the leadingedge; a compensating device operatively coupling said shaft and membersandincluding an upper fluid pressure means adapted to cause rotation ofthe shaft in a direction opposite said onedirection and a piping meansjoining the upper means together and, separately, joining the lowermeans together whereby to cause equalization of the lifting forcesacting on the blades to thus avoid flapping.

. In a preferred embodiment of the invention, :the shaft axes areparallel to and offset from the axes of the mem-.

bers in oppositedirections; the offset distance being such that the axesof said members are in line with'the axes of lift of the blades.

A better understanding of the invention will be afforded by thedescription that follows of a preferred embodiment having reference tothe appended drawing, wherein:

-FIG. 1 is a perspective view of a helicopter, shown in dotted lines,with the lifting construction of the invention illustrated in fulllines;

FIG. 2 is a perspective view, from below, showing on an FIG. 5 is across-sectional view through one lever of the hydraulic compensatingdevice;

FIGS. 6 and 7 are schematic views of a blade travelling against the windand with the wind, respectively;

FIG. 8 is a schematic view of a set of helicopter blades intended toillustrate the flapping effect.

The construction which is intended to be applied to a helicopter 1generally comprises a central lifting rotor 3 rotatable about a verticalaxis and a pair of blades 5, 5'

mounted on diametrically opposed sides of the lifting rotor 3 forrotation therewith; each blade having a leading edge 7 and an axis oflift 9 which is the locus of all centers of lift and extending parallelto the leading edge 7 of each blade. It will be noted that the saidleading edges 7 of the blades 5, 5 face in opposite directions.

The incidence angle of the blades 5, 5 is obtained by means of acollective pitch mechanism comprising rotary members 11, 11' mounted forsimultaneous limited rotation in reverse directions about an axisextending diametrically across the rotor 3; the said collective pitchmechanism being adapted, upon rotation of the rotary' on blades 5, 5' toavoid flapping, a compensating device,

preferably hydraulically operated, is provided for coupling shafts 13,13 and rotary members 11, 11', respectively, the said compensatingdevice including an upper fluid pressure means 15 and a lower fluidpressure means 17 (FIG. 5) for each blade, the said means being adaptedto cause rotation of shafts 13, 13 in either of two directions.

The compensating device also includes piping means 19 (FIG. 4), joiningthe upper means 15 together and piping means 19 joiningthe lower means17 together independently of piping means 19.

V Preferably, shafts 13 and 13' are not mounted in alignment with theaxes of their respective rotary members 11, 11 but offset therefrom asclearly shown in FIG. 2 and on a distance, in reverse directions, suchthat the axes of rotary members 11, 11' extend through the axes of lift9,

9' of blades 5, 5', respectively.

The construction of the rotor of the invention will now be given in moredetails.

The central lifting rotor 3 is formed of a vertical mast 21 at the upperend of which is mounted the rotor hub 23, the latter being connectedthereto by means of lateral axles 25, 25 which, as shown in FIGS. 2 and3, allow hub 23 to pivot relative to mast 21 about the inline transverseaxes of axles Z5, 25'.

As aforesaid, the collective pitch mechanism comprises the rotarymembers 11, 11' mounted for limited rotation or pivoting about adiametral axis of hub 23. Pivotal mounting of the rotary members 11, 11'may be through any conventional manner.

The collective pitch mechanism also includes a pair of radial arms 27,27 fastenedto rotary members 11, 11

"to extend in opposite directions as clearly illustrated in FIG. 3. Fromarms 27, 27' depend vertical operating rods 29, 29' which aresimultaneously operated by any suitable mechanism, not shown.

From the above description, it will be understood that the angle ofincidence of blades 5, 5' may be changed by actuating the. saidoperating rods 29,19 thus causing blades 5, 5 both to move upward ordownward from an upward position.

In the preferred case where shafts 13, 13 are mounted in offsetrelationship with respect to rotary members 11, 11 the collective pitchmechanism includes levers 31, 31 in the form of a heavy blade having oneend secured to 3,2 3 one of the rotary members 11, 11' while shafts 13,13 are rotatably mounted thereon in any conventional manner as thatshown in FIG. 3 at 33.

As a part of the hydraulically operated compensating deviceabove-mentioned there is provided two L-shaped elements 35, secured atone end to shafts 13, 13, respectively. The other end of the saidL-shaped levers 35, 35' respectively extend into generally U-snapednotches 3'7, 37 formed at the forward end of levers 31, d1,respectively. It will be noted that the ends of levers 35, 35' enteringinto the said notches 37, 37' are formed with two flat surfaces. 7

As best illustrated in FIG. 5, the upper fluid pressure means of eachlever 31 is a piston 39 displaceable in a cylinder 40 formed on theupper part of lever 31, the piston 39 having a piston rod 41 projectingout of cylinder 4%) and having the outer end thereof applied on the topface of L-shaped element 35. Cylinder 40 communicates with a fluidconduit 43 which is part of the upper piping means 19, previouslymentioned.

It will be understood from perusal of FIG. 5 that the lower fluidpressure means 17 is identical to the upper means 15 and, therefore,need not be described. It may only be added that its piston rod isapplied on the lower flat surface at the end of L-shaped element 35.

It will also be understood that what has just been described in relationto the upper and lower fluid pressure means applies for both levers 31and 31.

The outlets 45' of the upper fluid pressure means 45 of both levers 31,31' are interconnected by means of a flexible piping and, similarly, theoutlets 45 of the lower fluid pressure means are also interconnected bya flexible conduit (referred to in FIG. 4 by numerals 19, 19').

It should however be noted that the said flexible conduits areindependent of one another.

Finally, fluid pressure tubes 47, 47 are provided for supplying pressurefluid into the said flexible conduits respectively.

It should be pointed out at this time that the fluid provided throughtubes 47, 47' are always at the same pressure.

From the above description, the operation of the lifting construction ofthe invention can now be made.

Equal fluid pressure is applied against pistons 39 of the upper andlower fluid pressure means 15, 17 through tubes 47, 47'. Assuming thatthe angle if incidence of blades 5, 5 is changed by pullingsimultaneously on rods 29, 29 and bringing them down an equal amount,the lifting force due to the wind action acting on blades 5,

5 will increase but, as will be understood, a greater amount for blade 5moving against the wind than blade 5 moving with the wind. The action ofthe lifting force on blade 5 will cause an increase of pressure in thelower cylinder 40 of lever 31 and this increase pressure will in turnapply to the lower fluid pressure means 17 of blade 5 forcing thecorresponding L-shaped element 35' to move upwardly and blade 5' torotate counter-clockwise thus increasing the angle of incidence of thesaid blade 5' and amount corresponding to the increase in pressurebrought about by blade 5. The net result will be a greater angle ofincidence for blades 5' travelling with the wind than the correspondingangle of incidence of blade 5 travelling against the wind andequalization of the lifting forces acting on the two blades. Thissituation is illustrated in FIGS. 6 and 7 with the illustration of FIG.6 being that of blade 5 and that of FIG. 7, blade 5'. The positionsshown in dotted lines are those resulting from the above-describedaction.

As a result of the above action, blades 5 and 5' will tend to keep in ahorizontal plane as shown in full lines in FIG. 8 rather than attempt tomove sl-antwise as illustrated in dotted lines thus causing the flappingeffect described previously.

Although a specific embodiment has just been described,

it will be understood that various modifications may be made withoutdeparting from the spirit of the invention, the scope of which is to beconstrued from the appended claims.

I claim:

1. In a helicopter, a lifting construction therefore, comprising:

(a) a central lifting rotor;

(b) a rotary member mounted on an axis each side of said rotor unto ahub solidly fixed to said rotor;

(c) a blade mounted on each side of said rotor and having a leading edgeand an-axis of lift;

(d) a shaft secured at one end on the inboard end of each blade andpivotally mounted at the other end on a lever, the said lever beingsolidly fixed to one of said members, said shaft rotating about an axisparallel to and between said axis of lift and said leading edge;

(e) a compensating device operatively coupling said shafts and membersand including:

an upper fluid pressure means adapted to cause rotation of said shaftsin one direction;

a lower fluid pressure means adapted to cause rotation of said shafts ina direction opposite said one direction; and

a piping means joining said upper means together and another pipingmeans joining said lower means together independently of the firstpiping means whereby to cause equalization of the lifting forces actingon said blades to thus avoid flapping.

2. A lifting construction as claimed in claim 1, wherein said shaft axesare parallel to and offset from the axes of said members in oppositedirections; the offset distance being such that the axes of said membersare in line with the axes of lift of the blades.

In a helicopter, a lifting construction therefor, comprising:

(a) a central lifting rotor, rotatable about a vertical axis;

(b) a pair of blades mounted on diametrically opposed sides of saidrotor for rotation therewith; each blade having a leading edge and anaxis of lift; the leading edges of said blades facing in oppositedirections;

(c) a collective pitch mechanism including members rotatably mounted oneach side of a hub coaxially fixed to said rotor for simultaneouslimited rotation in reverse directions; said mechanism adapted, uponrotation of said members, to change the pitch of said blades;

((1) a shaft secured at one end on the inboard end of each blade andpivotally mounted at the other end on a lever, the said lever beingsolidly fixed to one of the said members, said shaft rotating about anaxis parallel to and between said axis of lift and said leading edge;

(e) a fluid pressure operated lift compensating device cooperativelycoupling said shafts and mechanism and including:

upper pressure means for each shaft adapted to cause rotation of saidshafts in one direction;

lower pressure means for each shaft adapted to cause rotation of saidshafts in a direction opposite said one direction, and

piping means joining said upper pressure means together and furtherpiping means joining said lower pressure means together independently ofthe other piping means, whereby to cause an equal fluid pressure to acton said upper and lower pressure means to thus equalize the liftingforces acting on said blade to avoid flapping.

4. A lifting construction as claimed in claim 3, wherein said shaftsaxes are parallel to and offset from the axes of said members inopposite directions; the offset distance being such that the axes ofsaid members are in line with the axes of lift of the blades.

5. In a helicopter, a lifting construction therefor, comprising:

(a) a central lifting rotor, rotatable about a vertical axis;

(b) a pair of blades mounted on diametrically opposed sides of saidrotor for rotation therewith; each blade having a leading edge and anaxis of lift; the leading edges of said blades facing in oppositedirections;

(c) a collective pitch mechanism including axle members mounted onopposite sides of said rotor for notation therewith about said verticalaxis; said axle members being also mounted for simultaneous limitedrotation in reverse directions about an axis extending diametricallyacross said rotor; said mechanism adapted upon rotation of said axlemembers to change the pitch of said blades;

(d) said mechanism further including a lever secured on each axle memberfor limited rotation therewith in a plane normal to the diametral axisof said axle members;

(e) a shaft secured on the inboard end of each blade and mounted on thecorresponding lever for rotation relative thereto about an axisextending parallel to, between said lift axis and said leading edge andoffset from the axis of said axle members;

(f) an L-shaped element fastened to each shaft and having a portionthereof projecting in a notch cut out of the corresponding lever;

(g) an upper and a lower hydraulic piston in each lever having pistonrods connected to two opposite sides of the portion of the correspondingelement adapted, upon rotation of the lever, to cause rotation of thecorresponding shaft, and.

(h) piping means joining said upper pistons together and said lowerpistons together, whereby to cause an equal fluid pressure to act onsaid upper pistons and said lower pistons to thus equalize the liftingforces acting on said blades to avoid flapping.

6. A lifting construction as claimed in claim 5, wherein the pipingmeans joining the upper pistons is under the same hydraulic pressure asthe piping means joining said lower pistons.

7. A lifting construction as claimed in claim 5, wherein said levers aremounted on said axle members to extend in opposite directions and avertically operated leverage mechanism is provided to cause simultaneousV rotation of said axle members in opposite directions of rotation.

References Cited by the Examiner FOREIGN PATENTS 7/1948 Great Britain.

MARK NEWMAN, Primary Examiner.

JULIUS E. WEST, Examiner.

1. IN A HELICOPTER, A LIFTING CONSTRUCTION THEREFORE, COMPRISING: (A) ACENTRAL LIFTING ROTOR; (B) A ROTARY MEMBER MOUNTED ON AN AXIS EACH SIDEOF SAID ROTOR UNTO A HUB SOLIDLY FIXED TO SAID ROTOR; (C) A BLADEMOUNTED ON EACH SIDE OF SAID ROTOR AND HAVING A LEADING EDGE AND AN AXISOF LIFT; (D) A SHAFT SECURED AT ONE END ON THE INBOARD END OF EACH BLADEAND PIVOTALLY MOUNTED AT THE OTHER END ON A LEVER, THE SAID LEVER BEINGSOLIDLY FIXED TO ONE OF SAID MEMBERS, SAID SHAFT ROTATING ABOUT AN AXISPARALLEL TO AND BETWEEN SAID AXIS OF LIFT AND SAID LEADING EDGE; (E) ACOMPENSATING DEVICE OPERATIVELY COUPLING SAID SHAFTS AND MEMBERS ANDINCLUDING: AN UPPER FLUID PRESSURE MEANS ADAPTED TO CAUSE ROTATION OFSAID SHAFTS IN ONE DIRECTION A LOWER FLUID PRESSURE MEANS ADAPTED TOCAUSE ROTATION OF SAID SHAFTS IN A DIRECTION OPPOSITE SAID ONEDIRECTION; AND A PIPING MEANS JOINING SAID UPPER MEANS TOGETHER ANDANOTHER PIPING MEANS JOINING SAID LOWER MEANS TOGETHER INDEPENDENTLY OFTHE FIRST PIPING MEANS WHEREBY TO CAUSE EQUALIZATION OF THE LIFTINGFORCES ACTING ON SAID BLADES TO THUS AVOID FLAPPING.